I agree with Number, it really just sounds like your next period is coming. If you do want to take a home test there is nothing to stop you from doing so, however. I might add that this is not an emergency in the sense that you would need to do something immediately and have to know right now or else it will be too late to do that thing. If you are pregnant (and don't fret, it doesn't sound like it), it is too late to take the morning-after pill. This would give you at least a few weeks to decide what to do. And if you are not pregnant, it is not an emergency either. Try to relax.
You should wait to test. It doesn't sound like your pregnant. You had sex on the start of your last period. He did not ejaculate in you. There may have been precum but he had a low sperm count. Chances of pregnancy are very slim.